Assigkob of one



(No Model.)

J. B. PITGHFORD.

VALVE GEAR.

No 342,035. Patented May 18, 1886.

NITED STATES PATENT tries.

JOHN B. PITCHFORD, OF SAN FRANCISCO, CALIFORNIA, ASSIGNOR OF ONE- HALFTO \VILLIAM T. GARRATT, OF SAME PLACE.

VALVE-GEAR.

SPBQIPIC'ATION forming part of Letters Patent No. 342,035, dated May 18,1886.

Serial No. 174,370. (No model.)

To all whom it may concern:

Be itknown that LJQHN B. PITCHFORD, of the city and county of SanFrancisco, State of California, have invented an Improvement inEngine-Valve Gear; and I hereby declare the following to be a full,clear, and exact de scription of the same.

My invention relates to certain improvements in the means for actuatingthe valve gear of engines. It consists in a novel 1nanner ofconstructing cams, and in their application for the working of thevalves of steamengines, so as to cut off the steam either at a fixedpoint in the stroke or at one which is I 5 automatically variable.

Referring to the accompanying drawings for a more complete explanationof my invention, Figure 1 is a longitudinal elevation with a partsection of a Corliss engine, showing the application of my device. Fig.2 shows the annular cam and the means for controlling it by acentrifugal governor. Fig. 3 is a section of the cam and rollers. Fig. 4is a perspective view of the equalizing-levers and arm of thesteam-valve stem. Fig. 5 shows the annular cam imparting movement to asliding bar.

A A are the equalizinglevers attached to the arms on the stems of thesteam valves. One end of each lever is connected by a rod,

M, to the rock-plate-such as is used in most of the Corliss cnginesandthe other ends of the levers A are connected to the levers B B. Theselevers B are fulcrumed on pins S, which are secured to the pillow-blockor other fixed portion of the frame. The lower ends of the levers B areconnected with a cam, by which they are caused to oscillate'about theirfulcrums, thus operating the levers A,so as to actuate the valves to cutoff the steam at the 40 proper time after it has been admitted by theaction of the rock-plate upon the valves and that of the regulareccentric by which the rockplate is moved.

In my invention I have shown an improved method of forming the cam. Itconsists of the solid portion D,which has its periphery turned orotherwise formed in the desired shape, after which a wrought-iron orsteel band, a, is shrunk upon it, being fitted to its curvature,

and having one edge projecting beyond the face of the part D so as toform a flange.

Upon the lower ends of the levers B are journaled the rollers G C, sothat one roller runs upon one side and the other upon the opposite sideof the flange or ring a. The irregular form of the cam acts upon theserollers and the lower end of the lever, so as to cause the latter tovibrate. One of the rollers has its pin fitted into a slotted hole inthe supportingarm, so that it may be adjusted to take up any wear fromtime to ti me,as shown at c, Fig. 2. By this construction,with therollers running upon opposite sides of the cam-flange, instead of asingle roller running in a grooved cam, I obtain the followingadvantage: When a single roller runs in a grooved cam it sometimes turnsin one direction and sometimes in the opposite direction, its rotationbeing reversed a number of times in each revolution, depending upon theform of the cam and the number of times that it changes the side of thegroove upon which it travels. This soon Wears the single roller Hat andimpairs its efficieney; but in my device the rollers always run in thesame direction, and consequently 5 wear but very little.

The cam is fitted loosely upon the engine shaft, and has a pinion, E,connected with it.

I prefer to bore the cam out, so as to receive a bronze or othersuitablebushing,wbich is fitted tightly into it, and which turns upon the shaft.

F isaquadranthaving its periphery toothed, and having a single armextending to the center, from which the curve is struck. This arm ispivoted to the disk or wheel, which is secured to the shaft upon theside of the cam, and it is connected by a link, I), with a weightedleverarm, c, which has one end pivoted to another portion of the disk.

The centrifugal action causes the weight to be thrown outward more orless, audit thus acts through the link upon the quadrant F, which inturn acts upon the pinion E, and thus turns the cam, so as to cause itto act through 5 the rollers 0 upon the lovers B and the valve gear.\Vhen the speed decreases, the weighted lever-arm is drawn back again bythe spring H, which is also connected at one end with the lever c and atthe other with the arm of the toothed quadrant F. The link whichconnects the weight with the quadrant is connected withthe quadrant at apoint between its periphery and its fulcrum, the spring .being connectedwith the quadrant-arm nearer to the fulcrum than to the weight. By thisarrangement the act-ion of the governor is exceedingly sensitive, as theweight moves but a short distance to cause the quadrant to act upon thepinion and cam sufficiently to regulate the engine.

The operation of the cam is as follows: While any portion of the curvewhich is concentric with the center is in contact with the rollers thelevers B will remain stationary; but when the cam is revolved so as tobring its irregular portion between the rollers it will impart a motionto the levers B equal to the difference in its-outline, and this motionis in turn communicated to the valves of the engine by anysuitableconnection or mechanism.

It will be manifest that the rollers C may be either applied at the endof the lever or levers B, as shown in Fig. 1, or they may be attached tothe sliding bars, which move in suitable guides, as shownin Fig. 5,which may be connected with the parts to be moved, the action beingessentially the same.

Having thus described my invention, what I claim as new, and desire tosecure by Letters Patent, is-

1. A'cain fitted to an engine-shaft so as to be rotated backward andforward around the shaft, said cam having a flange or rim projecting atright angles from one edge, in combination with a lever or sliding blockhaving plain-faced rollers pivoted thereto, so as to roll in contactwith the opposite sides of the flange, and an equalizing-lever havingits cen tral portion swinging upon a pin on the rockerarm or valve stem,by which the valve is moved, a rod connecting the upper end of saidportion suspended and swinging on a pin that is connected with the stemof a steam-valve, one end of said lever receiving motion from aneccentric or rock-plate, and the other end from one end of a secondlever having its central portion swinging upon a fixed fulcrum, incombination with an adjustable cam upon the engine-shaft, through whichthe opposite end of the second lever is reciprocated intermittently,substantially as herein described.

3. In an engine, a rotary valve and equalizing arm or lever, having itscentral portion swinging upon a pin on the rocker-arm, by which thevalve is moved, a fixed eccentric imparting motion to one end of theequalizinglever through suitable connections, in combination with anirregular cam adjustable upon the engine-shaft and a lever-arm turningupon the fulcrumpin in its central portion and having one end connectedwith the cam, so as to receive an intermittent motion from it, while theother end is connected with the end of the equalizing-lever opposite tothe one actuated by the fixed eccentric, substantially as hereindescribed. 7

In witness whereof I have hereunto set my hand.

JOHN B. PITCHFORD.

Witnesses:

S. H. NoURsE, H. ,0. LEE.

